Study to Assess the Effects of PTC857 Treatment in Participants With Amyotrophic Lateral Sclerosis ALS

Inclusion Criteria

• •ALS with preserved function, defined as:
• •1. Onset of the first symptom leading to the diagnosis of ALS ≤24 months at the time of the initial Screening Visit
• •2. Revised EL Escorial criteria of either:
• •(i) Clinically definite ALS (ii) Clinically probable ALS
• •A total ALSFRS-R score of at least 34 at the start of the Screening Period
• •No significant respiratory compromise as evidenced by slow vital capacity ≥60% at the start of the Screening Period
• •All chronic concomitant medications (both prescription and over the counter), and non-pharmacologic therapy regimens, excluding standard-of-care therapy riluzole, edaravone, or sodium phenylbutyrate/taurursodiol, should be stable and unchanged from 14 days prior to the start of the Screening Period and intend to remain stable and unchanged throughout the course of the study
• •Female participants must have a negative breast cancer imaging screening status (not considered clinically abnormal and/or requiring further evaluation/treatment) within 6 months prior to the Screening Visit, or during the Screening Period.
• •Standard-of-care therapy for the treatment of ALS (riluzole, edaravone, or sodium phenylbutyrate/taurursodiol) should be stable and unchanged from 30 (-3) days prior to the start of the Screening Period and intend to remain stable and unchanged throughout the course of the study.